The present invention relates to apparatus for winding wire about a core of toroidal shape and made from magnetizable material. The wound core may be an inductor in an electronic circuit, if only one wire is wound around it, or, in the case of two separate wires wound around it, it may be a transformer.
In the past, some machines have used a shuttle in the form of a thin needle for guiding and moving the wire along the axis of the toroid to "loop" the wire about the toroid.
In machines of this type, the size of the toroid is limited by the size of the shuttle since it must be allowed to pass through the center opening of the toroid in forming a loop.
With the current trend toward miniaturization and microminiaturization of electronic circuitry, this has been found to be a limitation. Thus, in particular, the present invention relates to apparatus and method for winding wire about a toroidal core without the need of a shuttle to carry the wire axially through the center opening in the toroid.
Briefly, the apparatus of the invention includes a lower support which may have a vertical slot and which is secured to a base or frame. The upper surface of the lower support is flat for receiving the toroid at a winding station such that the axis of the toroid is aligned with the vertical slot in the lower support.
The toroid is held against the lower support by an upper guide member which applies an axial force against the upper surface of the toroid. The toroid is further held at the winding station by a pair of movable jaws carried by an indexing mechanism which engage the outer surface of the toroid to apply a radial holding force.
To insert a toroid into the winding station, the upper support is raised manually and moved aside. Further, a push actuator releases the jaws to facilitate insertion of the toroid onto the upper surface of the lower support. When the toroid is inserted, the push actuator is released so that the jaws exert the radial holding force on the toroid, and the upper guide member is also returned to its operating position to clamp the toroid against the lower support. Preferably, the jaws are mounted to arms of leaf spring material so as to permit the jaws to accommodate themselves to the axially clamping motion of the upper guide member while maintaining their radial holding force on the toroid.
With the toroid thus held both radially and axially at the winding station, an operator places a wire axially through the center of the toroid. Beneath the toroid are a pair of draw rollers, one of which is continuously driven. While inserting the wire, it is guided toward the center opening of the toroid by a funnel-shaped guide surface in the upper guide member, and it is guided toward the draw rollers by the slot in the lower support. In the operating position, the draw rollers engage each other so that when the wire enters the nip between the draw rollers, it is pulled through the center of the toroid and drawn tight.
The machine is capable of being operated in either a "full cycle" mode, in which the operator may use a foot pedal or other switch for each complete loop that is formed about the toroid by the wire, or a "momentary contact" mode in which the operator uses a separate switch to actuate the mechanism for only that portion of a cycle during which the momentary contact switch is actuated.
Assuming that the machine is being operated in the full cycle mode, the operator then actuates the foot pedal switch, and a power source is engaged to release the axial clamp of the guide member on the toroid so that it is held only by the jaws.
The power source then drives the indexing mechanism and the jaws to rotate the toroid about its axis, while maintaining the toroid at the winding station. At this time, the wire is ejected from the draw rollers beneath the toroid so that the operator may easily grasp the free end of the wire and return it upwardly to the top of the guide member.
When the toroid is fully indexed, the power drive causes the jaws to release the toroid, and it also returns the upper guide to clamp the toroid axially. While the toroid is thus clamped at the winding station, the power drive returns the indexing mechanism to its starting position. When the indexing mechanism is returned to the starting position, the power drive mechanism again causes the jaws to clamp the toroid radially, and the mechanism is prepared for a new cycle. By operating the apparatus in the momentary contact mode, it is possible to cause the mechanism to go through any portion of a cycle that is desired, or to operate continuously, as long as the momentary contact mode switch is actuated.
With the present invention, an operator is able to form a complete loop of wire about a very small toroid in about a second, and the only limitation on the size of the toroid is the diameter of the wire being used. Since the core is indexed after each loop is formed, the wire is laid side-by-side about the toroid, which provides a more efficient packing of the wire in the center of the toroid and more uniform electrical characteristics of the core.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.